Abstract

Introduction

The aim of this analysis was to describe comprehensively the cross-sectional and longitudinal
patterns of analgesic and nutraceutical medication use for knee osteoarthritis (OA)
in a contemporary US cohort and to investigate associated demographic and clinical
factors.

Methods

Baseline, 12, 24 and 36 month data were obtained retrospectively from the National
Institutes of Health Osteoarthritis Initiative. Participants had symptomatic radiographic
knee OA. Multiple binary logistic regression models identified characteristics independently
associated with the use of analgesics or nutraceuticals.

Results

We included 987 subjects (55.9% female, mean age 61.5 years, 71.0% white). At baseline,
68.2% reported frequent use of a conventional analgesic or nutraceutical for joint
pain (for more than half of the previous month). Non-prescription non-steroidal anti-inflammatory
drugs (NSAIDs) were the most frequently reported medications (26.8%), even in those
more than 75-years old. Multiple conventional analgesics were used by 11.9%. Frequent
analgesic use was more likely in women (odds ratio (OR) 1.8 (95% confidence interval
(CI) 1.3 to 2.3)) and people with more pain (moderate 1.7 (1.2 to 2.4); severe 3.1
(2.1 to 4.7)); nutraceutical use was less likely in non-whites (0.4 (0.3 to 0.6)),
those more than 74-years old (0.6 (0.3 to 0.9)) and those with comorbidities (0.6
(0.5 to 0.9)) and more likely in people with Kellgren-Lawrence (KL) grade 4 (2.2 (1.5
to 3.3)). Overall there was no change in the proportion of participants frequently
using prescription or over the counter (OTC) analgesics at 36 months, although most
people had changed medication type; of those using a traditional analgesic at baseline
approximately one third were still using the same type at 36 months (ranging from
26.2% of baseline prescription NSAID users to 40.6% of baseline acetaminophen users).
All participants reporting baseline analgesic use also reported 36 month analgesic
use. Female participants (OR 95% CI 1.2 to 3.2, P = 0.009), those with high body mass index (1.2 to 4.8, P = 0.010) and those with moderate (1.6 to 2.6, P = 0.090) or severe (1.8 to 12.0, P = 0.002) baseline pain were more likely to use pain medication during the 36 month
follow-up period; participants more than 75-years old were less likely (0.2 to 1.0,
P = 0.053).

Conclusions

Most people with knee OA used pharmacological therapies frequently, and use appeared
to be according to American College of Rheumatology recommendations. Change in medication
type used was common. Persistent non-prescription NSAID use in older people is an
area of concern.